1. Field of the Invention
The present invention relates to a batch mixer for mixing material by rotating rotors in a chamber. More particularly, the present invention relates to a structure for controlling the internal temperature of the chamber (the temperature of a material to be mixed), which is raised during mixing, and further a structure for improving the fluidity of the material in the chamber.
2. Description of the Related Art
As conventionally known techniques for batch mixer, for example, a batch mixer is disclosed in Japanese Patent Application Laid-Open (Kokai) No. 9-220718. This mixer has a barrel which forms a cylindrical sealed chamber having a cross-section consisting of two mutually communicated circles, and two rotors housed in the barrel to mix a material by rotation, wherein the chamber has a first heat transfer passage on the outside of the chamber around each rotor, and extends between both axial ends of the chamber to circulate controlled fluid. The internal temperature of the chamber (the temperature of the material to be mixed) raised during mixing was controlled by such a structure.
However, the barrel inner wall of the batch mixer disclosed in Japanese Patent Application Laid-Open No. 9-220718 has a semi-cylindrical and smooth shape because the chamber diameter is constant. Consequently, the material under mixing are apt to slip on the contact surface with the barrel inner wall, which may make the contact surface difficult to renew. Namely, since the material is hardly evenly mixed in the vicinity of the contact surface, the temperature control of the material cannot be efficiently performed. Further, the temperature control is limited because of the limited contact area between the material and the barrel inner wall.